A. Field of the Invention
The present invention relates to a latitudinal sealing mechanism for use in a bag-packaging machine. More specifically, the present invention relates to a latitudinal seal mechanism for use in a bag-packaging machine that fills articles to be packaged in a bag while packaging the bag by sealing tubular packaging material longitudinally and latitudinally. The present invention also relates to such bag-packaging machine.
B. Description of the Related Art
There has been a longitudinal bag-packaging machine that fills articles such as foods to be packaged in a bag while manufacturing and packaging the bag.
For instance, a longitudinal pillow packaging machine forms a packaging material which is a sheet-shaped film into tubular shape by using a former and a tube. Longitudinal seal means (heat sealing) seals longitudinal edges of the tubular packaging materials that are placed one on top of another, thereby making bags. The pillow packaging machine fills articles to be packaged into the tubular packaging materials through the tube. Latitudinal sealing mechanism below the tube seals the upper portion of a bag and the bottom portion of an following bag. Then the pillow packaging machine cuts the middle of the latitudinally sealed portion. In such pillow packaging machine, operations of making a bag and filling articles in the bag occur in a continuous manner.
An example of such bag packaging machine is disclosed in Japanese Laid-Open Patent Application 10-86910. In the packaging machine disclosed therein, the tubular packaging material is sealed latitudinally by heating and pressing a pair of seal portions called seal jaws against each other, with the pair of seal jaws opposing each other across the conveyance path of the tubular packaging material. In a structure where the seal jaws simply repeat linear back and forth movements, the packaging material is sealed only at a point (a line). Therefore, conveyance of the packaging material has to be stopped while the packaging material is being sealed in this structure. To avoid this problem, each seal jaw is controlled by two kinds of motors, such that each seal jaw moves drawing a locus that is in the shape of letter D. In this way, enough sealing time is secured while conveying the tubular packaging material continuously, by having the seal jaws follow the tubular packaging material. Motors used in this bag packaging machine for controlling each sealing jaw include, a rotational motor for rotating each seal jaw, and a horizontal motor for moving each seal jaw horizontally back and forth.
Some of such mechanisms utilize a cam having a groove formed thereon, so as to engage inner and outer sides of a cam follower. U.S. Pat. No. 5,031,386 discloses one of such mechanisms. In this mechanism, a cam follower that supports a seal jaw engages a cam having a groove that is formed in the shape of the letter D. The cam follower and the seal jaw are supported by an end of a drive member fixed to a shaft. As the shaft rotates, the cam follower and the seal jaw move along the groove on the cam. In this manner, the seal jaw moves drawing a locus in the shape of letter D.
Although the aforementioned mechanism allows the seal jaw to move drawing a locus in the shape of letter D, the seal jaw and the cam follower need to be able to slide against the drive member, since the seal jaw moves drawing a locus in the letter of D instead of a circle while the drive member rotates.
However, it is structurally difficult to configure a sliding mechanism having bearings in the portion where sliding needs to occur. Consequently, the seal jaw and the cam follower have to slide against the drive member by contacting and slipping against the drive member. Furthermore, if multiple cam followers are coupled to the cam to increase the processing speed of the bag packaging machine, the mechanism is subject to even more strict space constraint. Also, as the processing speed of the bag packaging machine increases, the slip-sliding by the cam follower and the seal jaw against the drive member may lead to a durability problem of the latitudinal sealing mechanism.
Further, packaging materials are becoming thinner recently. Accordingly, more pressure is required to seal the packaging material. This causes a greater reactionary force in the structure that supports each seal jaw. Especially in the structure disclosed in the aforementioned applications, reactionary force occurs in the horizontal motor that moves each seal jaw horizontally back and forth. Consequently, the horizontal motor has to be able to generate a torque that is large enough to be able to oppose the reactionary force. In other words, the horizontal motor is required of extra functions that would not be necessary if the horizontal motor were simply moving seal jaws horizontally. Also, the rotational motor has to rotate each seal jaw (in a downward direction) pushing the seal jaw against the reactionary force applied to each seal jaw. Therefore, the rotational motor also needs to be able to generate torque that is comparable to the torque of the horizontal motor.
In the structure where two kinds of motors rotate each seal jaw so as to draw a locus in the shape of letter D and thereby generate sealing pressure, the magnitude of sealing pressure can be easily adjusted by adjusting the horizontal motor. On the other hand, such structure requires a high-powered motor that can generate torque comparable with the sealing pressure, which leads to a higher cost of the bag packaging machine.
In view of the above, there exists a need for an improved latitudinal seal mechanism for a bag packaging machine which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
The object of the present invention is to provide a latitudinal seal mechanism for use in a bag packaging machine that utilizes a cam, with the latitudinal seal mechanism allowing a seal portion to move drawing a locus in a shape other than a near circle having the shape of the letter D, without utilizing a structure in which the cam follower and the seal portion (seal jaw) slide against a coupling member (drive member) fixed to a rotational shaft (shaft).
In accordance with one aspect of the present invention, there is a latitudinal seal mechanism for use in a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The latitudinal sealing mechanism includes a seal portion, a fixed cam, a cam follower, a rotational shaft, a coupling member, and a shaft support portion. The seal portion is adapted to be heated and move circularly, such that the seal portion abuts on and moves away from the tubular packaging material. The fixed cam has a shape that corresponds to a locus of the movement of the seal portion. The cam follower supports the seal portion and is adapted to move along the fixed cam. The rotational shaft relatively moves the cam follower circularly about a rotational center of the rotational shaft. The coupling member couples the rotational shaft and the cam follower. The shaft support portion supports the rotational shaft such that the rotational shaft can move in a direction that crosses with a direction of an axial core of the rotational shaft.
The latitudinal seal mechanism moves the heated seal portion circularly, such that the seal portion seals the tubular packaging material by heat when the seal portion abuts on the tubular packaging material. The fixed cam has a shape that corresponds to the locus of the movement of the seal portion such that sealing conditions such as sealing time are satisfied. The sealing portion is supported by the cam follower which moves along the fixed cam. The cam follower moves drawing a predetermined locus, thereby sealing the tubular packaging material.
The cam follower is coupled to the rotational shaft via the coupling member. If the rotational shaft is fixed, the cam follower cannot move but circularly. Therefore, in the latitudinal seal mechanism of the present invention, the shaft support portion supports the rotational shaft such that the rotational shaft can move in a direction that crosses with the direction of the axial core (direction of length), for instance in a perpendicular direction. In other words, in a conventional latitudinal seal mechanism, the cam follower and the coupling member had to slide against each other to allow the cam follower to move in a non-circular manner along the fixed cam. On the other hand, in the latitudinal seal mechanism of the present invention, the rotational shaft moves relative to the fixed cam, unlike the conventional rotational shaft which is fixed to the fixed cam. When the rotational shaft is movably supported, there is relatively more flexibility as to where the shaft support portion should be disposed. Also, since there is larger space in which the shaft support portion can be disposed, the shaft support portion can include a slide mechanism having rollers, or a pendulum-type support mechanism.
Therefore, the present invention eliminates conventional structure where the coupling member fixed to the rotational shaft slides against the cam follower and the seal portion. In this way, the present invention provides a more durable, desirable structure that can make the seal portion move drawing a locus other than a circle, such as one in the shape of letter D.
In accordance with another aspect of the present invention a latitudinal seal mechanism is adapted for use in a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The latitudinal sealing mechanism includes a pair of seal portions, fixed cams, cam followers, rotational shafts, coupling members, and shaft support portions. The pair of seal portions is adapted to be heated and move circularly, such that the seal portions hold the tubular packaging material therebetween. The fixed cams have shapes that correspond to a locus of the movement of each of the seal portions. The cam followers each support the seal portion, and are adapted to move along the fixed cams. The rotational shafts relatively move the cam followers circularly about rotational centers of the rotational shafts. The coupling members couple the rotational shafts and the cam followers. The shaft support portions support the rotational shafts such that the rotational shafts can move in a direction that crosses with direction of the axial core of the rotational shaft.
In this latitudinal seal mechanism, the heated pair of seal portions moves circularly, and closes the packaging material by heat by holding the tubular packaging material therebetween. The latitudinal seal mechanism utilizes fixed cams having shapes that correspond to the locuses of the movement of the seal portions, such that the sealing conditions such as sealing time are satisfied. Each seal portion is supported by the cam follower that moves along the corresponding fixed cam. The seal portions move drawing predetermined locuses, thereby sealing the tubular packaging material.
The cam followers are coupled to the rotational shafts via the coupling members. If the rotational shafts are fixed, the cam followers cannot move but circularly. Therefore, in the latitudinal seal mechanism of the present invention, the shaft support portion supports the rotational shafts such that the rotational shafts can move in directions that cross with the directions of the axial cores, for instance in a perpendicular direction. In other words, in a conventional latitudinal seal mechanism, the cam followers and the coupling members had to slide against each other to allow the cam followers move in a non-circular manner. On the other hand, in the latitudinal seal mechanism of the present invention, the rotational shafts move relative to the fixed cams, unlike the conventional rotational shafts which are fixed to the fixed cams. Therefore, when the rotational shafts are movably supported against the fixed cams, there is relatively more flexibility as to where the shaft support portions should be disposed. Also, since there is larger space in which the shaft support portions can be disposed, the shaft support portions can include a slide mechanism having rollers, or a pendulum-type support mechanism.
Therefore, the present invention eliminates conventional structure where the coupling members fixed to the rotational shafts slide against the cam followers and the seal portions. The present invention provides a more durable, desirable structure that can make the seal portion move drawing a locus other than a circle, such as one in the shape of letter D.
Preferably, in the latitudinal seal mechanism, at least two of the cam followers are disposed for each fixed cam. First and second cam followers, out of all the cam followers, are disposed on opposite sides of the rotational shaft with the rotational shaft therebetween. The first and second cam followers are supported by ends of the coupling member, with a middle portion of the coupling member being fixed to the rotational shaft.
Since a plurality of cam followers is disposed for each fixed cam, sealing can be conducted multiple times per one rotation of the rotational shaft. Consequently, the bag packaging machine will be more effective (speedy).
Also, in this embodiment, the first and second cam followers are disposed so as to hold the rotational shaft therebetween. Then, the first and second cam followers are coupled by the coupling member. Therefore, the cam followers move along the fixed cams even when the fixed cam is a plate cam that engages only an inner side of the cam follower, instead of a groove cam having a groove that couples both inner and outer sides of the cam follower. In other words, the cam followers do not disengage the fixed cams, even when the fixed cam is a plate cam. By allowing the rotational shaft to move relative to the fixed cam and couple the first and second cam followers to the rotational shaft via the coupling member, the fixed cam can use a plate cam which has a simpler structure than a groove cam.
Preferably, in the latitudinal seal mechanism, the fixed cams have such shapes that make the pair of seal portions move drawing locuses that have approximately the shapes of letter D and inverted letter D.
Since the pair of seal portion moves drawing the locuses that have approximately the shapes of letter D and inverted letter D, the seal portions can hold the tubular packaging material therebetween while they move approximately linearly. Therefore, the pair of seal portions can seal the packaging material for a predetermined sealing time even while the tubular packaging material is being conveyed.
Preferably, in the latitudinal seal mechanism, the rotational shafts repeat stopping and linear back and forth movement as they rotate, due to movement of the cam followers coupled to the fixed cams.
When the rotational shafts are supported by the shaft support portions so as to allow the rotational shafts to slide linearly, the rotational shafts repeat stopping and linear back and forth movement, as the seal portions move drawing locuses other than a circle such as ones in the shapes of letter D.
Preferably, the rotational shafts repeat stopping and arc-shaped back and forth movement as they rotate, due to movement of the cam followers coupled to the fixed cams.
When the rotational shafts are supported by the shaft support portions so as to allow the rotational shafts to slide drawing an arc, the rotational shafts repeat stopping and arc-shaped back and forth movement, as the seal portions move drawing locuses other than a circle such as ones in the shapes of letter D.
Preferably, the rotational shafts are rotatably supported by bearings. The shaft support portions support the bearings such that the bearings can move in a direction that cross with the direction of the axial core of the rotational shaft.
The bearings for rotatably supporting the rotational shafts are movably supported by the shaft support portions. Therefore, the shaft support portion can utilize a support mechanism in which the bearings slide linearly with little friction, or in which the bearings support the rotational shaft via an arm such that the bearing can move in the shape of an arc.
Preferably, each of the fixed cams includes an elongated bore formed thereon. The rotational shafts pass through the elongated bores of the fixed cams.
The fixed cams include an elongated bore, which is an elongate opening. Therefore, the rotational shafts that move relative to the fixed cams can cross with the fixed cams. Consequently, there is more flexibility as to where to dispose the shaft support portions that support the bearing. There is also larger space in which the shaft support portion can be disposed. Therefore, the shaft support portion can utilize a durable mechanism such as a slide mechanism having rollers or pendulum type support mechanism.
In accordance with still another aspect of the present invention there is a latitudinal seal mechanism for use in a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The latitudinal sealing mechanism includes a seal portion, a fixed cam, a cam follower, a rotational shaft, and a coupling member. The seal portion is adapted to be heated and move circularly, such that the seal portion abuts on and moves away from the tubular packaging material. The fixed cam has a shape that corresponds to a locus of the movement of the seal portion. The cam follower supports the seal portion and is adapted to move along the fixed cam. The rotational shaft relatively moves the cam follower circularly about a rotational center of the rotational shaft. The coupling member couples the rotational shaft and the cam follower. The rotational shaft is adapted to move in a direction that crosses with a direction of its axial core due to movement of the seal portion and cam follower.
In the latitudinal seal mechanism, the heated seal portion moves circularly, and seals the tubular packaging material by heat when the seal portion abuts thereon. The shape of the fixed cam corresponds to the shape of the locus of the seal portion, such that sealing conditions such as sealing time are satisfied. The seal portion is supported by the cam follower that moves along the fixed cam. The seal portions move drawing predetermined locus, thereby sealing the tubular packaging material.
The cam follower is coupled to the rotational shaft via the coupling member. If the rotational shaft is fixed, the cam follower cannot move but circularly. Therefore, in the latitudinal seal mechanism of the present invention, the rotational shaft is supported such that the rotational shaft can move relative to the fixed cam in a direction that crosses with the direction of the axial core, for instance in a direction perpendicular to the direction of the axial core. In other words, in a conventional latitudinal seal mechanism, the cam follower and the coupling member had to slide against each other to allow the cam follower to move in a non-circular manner. On the other hand, in the latitudinal seal mechanism of the present invention, the rotational shaft moves relative to the fixed cam, unlike the conventional rotational shaft which is fixed to the fixed cam. Therefore, when the rotational shaft is movably supported against the fixed cam, there is more flexibility as to where the shaft support portion should be disposed. Also, since there is larger space in which the shaft support portion can be disposed, the shaft support portion can include a slide mechanism having rollers or a pendulum-type support mechanism.
Therefore, the present invention eliminates conventional structure where the coupling member fixed to the rotational shaft slides against the cam follower and the seal portion. The present invention provides a more durable, desirable structure that can make the seal portion move drawing a locus other than a circle, such as one in the shape of letter D.
In still another aspect of the present invention there is a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The bag packaging mechanism includes forming means, a packaging material conveyance mechanism, a longitudinal seal mechanism, and a latitudinal seal mechanism. The forming means forms a sheet-shaped packaging material supplied thereto in tubular shape while receiving the articles to be packaged. The packaging material conveyance mechanism conveys the tubular packaging material in a downward direction. The longitudinal seal mechanism seals in a longitudinal direction overlapping portions of the tubular packaging material conveyed thereto. The latitudinal seal mechanism is a latitudinal seal mechanism described above, and seals in a latitudinal direction portions of the tubular packaging material conveyed thereto with a predetermined distance therebetween.
In still yet another aspect of the present invention there is a latitudinal seal mechanism of a bag packaging machine, where the horizontal motor does not oppose the sealing pressure and therefore can be reduced in size. Alternatively, the latitudinal seal mechanism does not utilize a horizontal motor but generates sealing pressure, in which the sealing pressure can be configured.
In accordance with still another aspect of the present invention there is a latitudinal seal mechanism for use in a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The latitudinal sealing mechanism comprises a pair of seal portions, a pair of partial cams, and partial cam followers. The pair of seal portions is adapted to be heated and move circularly, such that the seal portions hold the tubular packaging material therebetween. The pair of partial cams has a shape that corresponds to a locus that the pair of seal portions draws when the pair of seal portions holds the tubular packaging material therebetween. The pair of fixed cams makes the pair of seal portions press against each other. Each of the partial cam followers is supported by the pair of seal portions. The partial cam followers engage corresponding partial cams when the pair of seal portions holds the tubular packaging material therebetween.
This latitudinal seal mechanism moves the heated pair of seal portions circularly, such that the seal portions crimp by heat (seal) the tubular packaging material by holding the tubular packaging material therebetween. This latitudinal seal mechanism also includes a pair of partial cams and partial cam followers for securing sealing pressure. Each of the partial cam followers engages the partial cam.
The partial cam follower is supported by the seal portion. As each of the seal portions moves circularly, the partial cam followers engage the partial cams shortly before the pair of seal portions holds the tubular material, while the pair of seal portions holds the tubular material therebetween, and shortly thereafter. The pair of seal portions crimps the tubular packaging material by heat through pressure applied from the partial cams via the partial cam followers, while the partial cam followers engage the partial cams.
Here, the reactionary force that occurs in the seal portions during the sealing is applied to the partial cams via the partial cam followers. Therefore, by fixedly disposing the partial cams and/or by allowing the partial cams to generate force that opposes the reactionary force of the seal portions, the driving means that move the seal portions circularly are not affected by the reactionary force of the seal portions.
Preferably, the latitudinal seal mechanism should comprise pressure means for applying pressure to the partial cams such that the pair of seal portions press against each other when the pair of seal portions holds the tubular packaging material therebetween.
The reactionary force of the seal portions applied to the partial cams via the partial cam followers is at equilibrium with the pressure applied from the pressure means to the partial cams. Therefore, while the pair of seal portions holds the tubular packaging material therebetween, the seal portions are pressed against each other. In this manner, the tubular packaging material can be sealed securely with a predetermined pressure.
By allowing the pair of seal portions to separate from each other while the pressure means does not apply pressure to the partial cams, pressure can be applied by the pressure means to the partial cams only when the tubular packaging material needs to be sealed. When the tubular packaging material does not need to be sealed, for instance when the quality of articles to be packaged is not guaranteed, the pressure means can be configured not to apply pressure to the partial cams. In this manner, substandard articles can be thrown away before they are packaged.
Preferably, the latitudinal seal mechanism should comprise pressure adjustment means for adjusting the magnitude of pressure that the pressure means applies to the partial cams.
By adjusting the magnitude of pressure that the pressure means applies to the partial cams, the pressure by which the seal portions press against each other, in other words the sealing pressure can be adjusted. In this manner, besides that the sealing pressure can be secured by the partial cams and the partial cam followers, the sealing pressure can also be adjusted by the pressure adjustment means.
Preferably, in the latitudinal seal mechanism, the pair of partial cams is connected via a link mechanism. The pressure means applies force to a portion of the link mechanism in a direction that crosses with a direction in which the pair of seal portions is pressed against each other.
Here, the link mechanism connects the partial cams. The sealing pressure is generated by applying pressure to a portion of the link mechanism. Therefore, only one pressure means generates sealing pressure for partial cams, instead of having to dispose pressure means for each partial cam.
In this mechanism, the pressure means applies pressure not in a direction in which the pair of seal portions is pressed against each other (sealing pressure direction), but in a direction that crosses with the sealing pressure direction). In this manner, greater sealing pressure can be generated with smaller pressure.
Preferably, in the latitudinal seal mechanism, the pair of partial cam includes on each opposing surface an entrance surface, a pressure surface, and an exit surface. The pressure surface is formed immediately below the entrance surface. The exit surface is formed immediately below the pressure surface. The pair of seal portions receives no pressure applied thereto while the partial cam followers engage the entrance surfaces. The pair of seal portions is pressed against each other while the partial cam followers engage the pressure surfaces. The pair of seal portions receives no pressure applied thereto while the partial cam followers engage the exit surfaces.
As the partial cam followers supported by the seal portions that move circularly approach the partial cams, the partial cam followers first contact and engage the entrance surfaces. At this point, the pair of seal portions is apart from each other. Therefore, the tubular packaging material receives no pressure applied thereto.
As the seal portions are passed downward, and as the partial cam followers engage the pressure surfaces, the pair of seal portion is now pressed against each other. The tubular packaging material is sealed while the partial cam followers engage the pressure surfaces.
As the seal portions are passed further downward, the partial cam followers now engage the exit surfaces. The pair of seal portions separates.
By disposing the entrance and exit surfaces above and below the pressure surface, the partial cam followers can engage and disengage the partial cams smoothly. Therefore, the drive means does not need to output much power to move the seal portions.
Preferably, the latitudinal seal mechanism further comprises a pair of fixed cams, cam followers, and driving means. The pair of fixed cams has a shape corresponding to a locus of each of the pair of seal portions. The cam followers are adapted to support the seal portions and move such that the seal portions are engaged with the fixed cams. The driving means moves the cam followers.
In this latitudinal seal mechanism, the heated pair of seal portions moves circularly, and seals the tubular packaging material by holding the tubular packaging material therebetween. A locus of the seal portions is designed to meet desired sealing conditions such as sealing time. The latitudinal seal mechanism utilizes fixed cams having a shape that corresponds to the locus of the seal portions, such that the seal portions move drawing the locus. Each seal portion is supported by a cam follower that moves along a fixed cam such that the cam follower remains engaged with the fixed cam. In this manner, the seal portions move drawing the predetermined locus, thereby sealing the tubular packaging material.
In the aforementioned arrangement where the fixed cams and the cam followers make the seal portions move so as to draw a predetermined locus, the partial cams and partial cam followers secure sealing pressure, as well as enable easy adjustment of sealing pressure.
Preferably, in the latitudinal seal mechanism, the cam follower supports the seal portion via an elastic member that extends when the partial cam follower engages the partial cam.
In this latitudinal seal mechanism, the seal portion moves along the fixed cam with the elastic member therebetween. When the partial cam follower engages the partial cam, the elastic member extends, such that the cam follower remains engaged with the fixed cam. Even if reactionary force occurs in the seal portions that press against each other, the reactionary force is transmitted to the partial cams via the partial cam followers. Therefore, the reactionary force does not affect the elastic members, cam followers, or fixed cams.
More specifically, the latitudinal seal mechanism includes cam followers that move so as to remain engaged with fixed cams. However, the cam followers alone cannot make the seal portions contact each other; there always remains a gap between the seal portions as long as the seal portions are supported only by the cam followers. The latitudinal seal mechanism also includes partial cam followers and partial cams. The partial cam followers and partial cams are disposed such that the seal portions are pressed against each other when the partial cam followers engage the partial cams. While the partial cam follower engage the partial cams, the seal portions are supported by the partial cams, instead of the fixed cams.
Preferably, in the latitudinal seal mechanism, the driving means moves the cam followers via a rotational shaft and a coupling member. The driving means member is adapted to rotate the rotational shaft. The rotational shaft is adapted to rotate the cam follower relatively circularly about a rotational center of the rotational shaft. The coupling member connects the rotational shaft and the cam follower. The rotational shaft is adapted to move relative to the fixed cam in a direction that crosses with a direction of the length of the rotational shaft, due to movement of the seal portion and the cam follower.
The cam followers are coupled to the rotational shafts. If the rotational shafts are fixedly coupled, the cam followers cannot move but circularly. However, in this latitudinal seal mechanism, the rotational shafts can move in a direction that crosses with the direction of the length thereof, for instance in a direction perpendicular to the direction of the length thereof.
Preferably, in the latitudinal seal mechanism, the pair of seal portions rubs the tubular packaging material through a movement of said cam followers with a predetermined gap maintained between the pair of seal portions, before the partial cam followers engage the partial cams. The pair of seal portions also seals the tubular packaging material by holding the tubular packaging material therebetween while the partial cam followers engage the partial cams.
In this latitudinal seal mechanism, the pair of seal portions rubs the tubular packaging material with a predetermined gap maintained between the pair of seal portions, before the tubular packaging material is sealed latitudinally. This rubbing is achieved by the cam followers moving along the fixed cams. Since the tubular packaging material is rubbed before it is sealed, articles that are in the sealing portion of the tubular packaging material are pushed downward. Consequently, improper sealing that occurs due to articles sealed with the sealing portion of the tubular packaging can be avoided.
On the other hand, the tubular packaging material has to be pressed against each other to seal properly. This pressing operation is achieved by the partial cams and partial cam followers.
Preferably, in the latitudinal seal mechanism, a speed at which the driving means moves the cam follower while the pair of seal portions rubs the tubular packaging material is faster than a speed at which the driving means moves the cam follower while the pair of seal portions holds the tubular packaging material therebetween.
Since the speed at which the seal portions rub the tubular packaging portion is faster than the speed at which the tubular packaging material is sealed, there is enough area in which the tubular packaging material is rubbed.
In accordance with still another aspect of the present invention there is a bag packaging mechanism that fills articles to be packaged while sealing a tubular packaging material in longitudinal and latitudinal directions. The bag packaging mechanism comprises forming means, a packaging material conveyance mechanism, a longitudinal seal mechanism, and a latitudinal seal mechanism. The forming means forms a sheet-shaped packaging material supplied thereto in tubular shape while receiving the articles to be packaged. The packaging material conveyance mechanism conveys the tubular packaging material in a downward direction. The longitudinal seal mechanism seals in a longitudinal direction overlapping portions of the tubular packaging material conveyed thereto. The latitudinal seal mechanism is a latitudinal seal mechanism described above, and seals in a latitudinal direction portions of the tubular packaging material conveyed thereto with a predetermined distance therebetween.
These and other objects, features, aspects and advantages of the present invention will become more fully apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings where like reference numerals denote corresponding parts throughout.